The present invention relates to replacement or rehabilitation of existing underground pipe.
Underground pipes, such as gas, sewer or water mains periodically need replacement or rehabilitation due to leakage caused by cracks if increased service capacity is needed. Replacement or rehabilitation of underground pipes is traditionally cumbersome, in part, because often times the underground pipe must be unearthed for removal.
Methods and equipment have been developed which facilitate the replacement of underground pipe without the need to unearth the entire length of pipe. Such methods and apparatus are described in, for example, U.S. Pat. No. 4,789,268 to Yarnell and U.S. Pat. No. 4,738,565 to Streatfield. As best illustrated in FIG. 1, each of these methods involve digging trenches 14 and 15 on opposite sides of a section of pipe 16 which needs replacement. It is not uncommon for such trenches to be 10-30 feet deep in practice with lengths of 14 feet and widths of six feet or more. A frustro-conical section 10, having a constant tension guide cable 12 attached at one end, is passed through the section of pipe 16 being replaced. Guide cable 12 is also attached to a winch. Pipe 16 is cracked and/or fragmented with the fragments or pieces pushed into the surrounding earth, and a new plastic or flexible pipe 11 pulled into place. This process is commercially known as pipe bursting.
The operation extends from trench 14, to trench 15 and completely replaces the pipe therebetween. Each trench provides a location from which the pipe fracturing apparatus may be launched or inserted and then retrieved or removed. The methods and apparatuses of both U.S. Pat. No. 4,789,268 to Yarnell and U.S. Pat. No. 4,738,565 to Streatfield eliminate the need to completely dig up the old pipe in order to replace it. Because trenches 14 and 15 do not extend the length of pipe 16 this method is less expensive and less intrusive into the community served by the original pipe.
The xe2x80x9ctwo trenchxe2x80x9d method illustrated in FIG. 1 may also be used to line old pipe 16 with a slip liner pipe. The plastic liner operates to prevent leakage but has the drawback that the repaired main typically has a decreased capacity. Because lining the pipe generally decreases the capacity of pipe 16, the above described method of replacement or pipe bursting is often preferred.
Despite the convenience of the prior art over digging the old pipe out, the prior art methods still involve a degree of intrusiveness to the community because of the two adjacent trenches. Therefore, a need has arisen to decrease the inconvenience of replacing or rehabilitating pipe.
The present invention relates to a method of replacing existing or relining underground pipe. The existing pipe is surrounded by soil and includes a lumen and an associated longitudinal axis. The method includes the steps of forming a diagonal pilot hole between the existing pipe and an upper ground surface, forcing a ramming and fracturing tool through the pilot hole and existing pipe, where the ramming and fracturing tool is operative in placing a new pipe having an associated longitudinal axis so that the associated longitudinal axis of the new pipe is substantially the same as the longitudinal axis of the existing pipe. The section of pipe to be replaced generally runs from manhole to manhole.
The method of the present invention may also include the step of passing a guide cable having a proximal end and a distal end through the existing pipe and pilot hole. The proximal end of the cable is attached to a winch, and the distal end of the cable is attached to the ramming tool, so that the guide cable guides the ramming tool through the existing pipe and maintains an assistive force to the tool to provide a constant pressure against the pipe to be broken. After the existing pipe has been replaced, the ramming tool and guide cable may be removed through a manhole.